Diffusion of the spin probe perchlorotriphenylmethyl into the solvent-saturated porous catalyst support prepared from two types of aluminium oxide (Al2O3) and into pure solvent (CCl4) is studied by EPR imaging. By comparison of the experimental tomograms (spectra in nonuniform magnetic field) with the computed ones obtained on : the basis of the Fick’s diffusional equation solution, the effective diffusion coefficients D-e are determined and values of tortuosity are estimated. Two-dimensional spatial distribution of spin probe 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl at different times of diffusion into alumina support are detected and D-e is estimated to be less than 6 x 10(-8) cm(2)/s.